incentive
Espionage is often described as an arms race. What does that mean for gchq ?
In WWII, it was mathematicians following orders vs. mathematicians trying to outwit johnny foreigner. Easy to see who's going to win there (and we have no information about how well johnny foreigner managed to penetrate our brave eggheads).
Currently, it's people being paid by the hour trying to outdo : terrorists whose lives / life missions depend on their methods, and enthusiasts (hackers, cryptogeeks, whatever you want to call them) who see it as a game.
The smart money's not on the government any more.